function load_md() {
    var xmlhttp;
    if (window.XMLHttpRequest) {
        //  IE7+, Firefox, Chrome, Opera, Safari 浏览器执行代码
        xmlhttp = new XMLHttpRequest();
    }
    else {
        // IE6, IE5 浏览器执行代码
        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    xmlhttp.onreadystatechange = function () {
        if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
            //document.getElementById("markdowneditor").innerHTML = xmlhttp.responseText;
            mde.setMD(xmlhttp.responseText);
        }
    }
    xmlhttp.open("GET", "/README", true);
    xmlhttp.send();
}
